It is known to construct frames for vehicles such as automotive vehicles with longitudinal rails. The longitudinal rails of the vehicle must provide adequate load carrying capacity in order to minimize dash and toe-pan intrusion in the event of a frontal impact. As such, the longitudinal rails are typically made of steel.
It is desirable to reduce mass of a structure in vehicle body and chassis applications such as rails for a vehicle. However, longitudinal rails must have a desired stiffness and reducing the mass of these rails results in reduced stiffness of the rails.
It has been suggested to use a light-weight material such as aluminum to reduce the mass of the structure such as a rail. Boxed aluminum beams have the opportunity to reduce weight by as much as 30% over boxed steel beams if additional section height is available. However, if the exterior section size of the rail is constrained, aluminum offers no mass savings advantage over steel because three times the volume of steel is needed to obtain the required bending stiffness.
It has also been suggested to use different gage thicknesses where needed to achieve a light-weight design. Currently, there are two kinds of commercial tailor sheet metal blanks used to achieve the light-weight designed vehicle structures. One is “Tailor Welded Blank (TWB)”, which requires welding two or more different gage blanks together. The other one is “Tailor Rolled Blank (TRB)”, which uses rollers to compress the coil blank in a controllable manner to achieve variable thickness in the longitudinal direction. These two tailor blanks can be purchased as pre-form blanks with some cost premium over the original coil blanks.
As a result, it is desirable to provide a variable thickness member or blank to achieve the desirable thickness reduction where needed for a longitudinal rail of a vehicle. It is also desirable to provide a blank that does not require welding and has no discontinuity at a weld line for a longitudinal rail of a vehicle. Therefore, there is a need in the art to provide a new cost effective variable thickness member for a vehicle that meets these desires.